Hydraulic control system for weighing

ABSTRACT

An hydraulic bypass control system for tapping off the lift circuit of an hydraulically operated lifting device. The bypass control system slowly releases hydraulic fluid from the lift circuit and directs it back to the reservoir in a controlled manner so a load is smoothly moved from a reference position to a weighing position. Reliable weighing may be obtained by avoiding dynamic shaking, vibration and pressure surges, which permits the weighing step to be reliably made at the same point or range and affords precise calibration of a load transducer with a weighing instrument to be made.

This application is a division of Ser. No. 07/488,679, filed Mar. 5,1990, now U.S. Pat. No. 5,065,828.

BACKGROUND OF THE INVENTION

The invention is generally directed toward weighing refuse collected bya refuse collecting vehicle. The invention is more particularly directedtoward statically or dynamically obtaining the accurate weight of refuseloaded by hydraulically driven lifting arms of a refuse collectionvehicle. The invention is further focused on the utilization of anhydraulic bypass system for controlling the movement of the arms of anhydraulic lift system of a refuse vehicle through a defined measuringrange whereby a microprocessor converts electrical analog input signalsfrom a transducer and digitally converts the input to serially totaltare weights over time.

The immediate concerns of society include the need for effectivelytreating and disposing refuse of all kinds, including solid municipalwaste, particularly for landfill burial. Refuse haulers are usuallycontracted to collect refuse containers from commercial, factory andother business sites on a regular basis. When the containers are due forcollection, the refuse vehicle engages the container and dumps it into areceptacle that is part of the vehicle. In order for scavenger or wastehauling companies to dump loads at landfills, a per ton charge istypically assessed. While in the more crowded areas of the country,charges at the rate of $130.00 per ton are not uncommon, they usuallyfall in the range of about $30.00 to about $40.00 per ton. These chargesand others are borne by the customer and the waster hauler will add anincremental amount more as profit. Therefore it is critical to both thecustomer and the hauler to know what amount is charged for the refuseand waste landfill fees.

It is difficult to estimate costs when different amounts might becollected from a customer on an ongoing basis. The volume and weight ofrefuse discarded may vary from week to week in a wide range,particularly for industrial plants where waste might vary from metal orwood to light plastics. Also, in bidding on jobs, a waste hauler mightestimate too high or low. Estimating purely on the basis of volume isillogical because the charges for dumping at a landfill are made on aper ton basis. Thus the customer might be paying too much or too littledepending upon its particular business and how the waste hauler sets itscharges. These problems have been variously addressed in the prior artand proposed solutions usually involve weighing a container picked up byrefuse vehicle when it is full and then when it is empty.

Typical refuse collection vehicles are usually of the type that haveeither a front loading or a rear loading set of hydraulic arms that arejoined to extending engagement arms for engagement with engageablesleeve-like portions of the containers. The pivotal lifting arms areusually in the shape of a large downward yoke or U-shape and two sucharms typically pivotally straddle the front of the cab or the rear ofthe refuse vehicle.

Hydraulic lift cylinders may either pull or push the arms during liftingdepending upon the mechanism. The engagement arms are aligned with theengageable portions of the container and the refuse vehicle operatorpositions the vehicle while at the same time working the hydraulicsystem to engage the container. Then, the lift arms are drivinglypivoted and the container is lifted and leveled as it travels upwardlyto be ultimately dumped into the receptacle of the vehicle.

Typical weighing procedures involve the use of load cells or transducersproviding analog electrical signals proportionate to the loading sensed.The signals are converted by an analog/digital converter and may betabulated and stored by a microprocessor.

The utilization of transducers in the form of load cells is shown inU.S. Pat. No. 4,714,122 wherein the transducer is mounted on the liftingelement of a refuse truck. The signal is generated when the container isat a certain point relative to the truck body by virtue of a sensingswitch activated by a cam surface on the lifting arms. However, loadcells have been found to be unreliable and are easily damaged. Thedynamics in lifting heavy weights creates significant vibration,stuttering and unsteadiness as the lift arms in the powerful hydraulicsystems of a refuse vehicle are operated. Waiting for vibration andshaking to stop in order to make an accurate weighing wastes costlyminutes, even for static measurements. Accuracy is naturally moredifficult should dynamic weighing be attempted as the load is in motion.

Another use of load cells as found in U.S. Pat. No. 4,645,018, whereinthe gross weight and the empty weight of the container are determinedwhile the container is being emptied. A strain gauge (load cell) sets ina sliding body that is arranged with the lifting arms so that thesliding body will transmit the value of the weight of the refusecontainer to the load cell while it is displaced downwardly. The lockingdevice is to be released and the dead weight of the container ismeasured by the load cell at the empty position. The signals for theindividual full and empty weights are electrically communicated to adata recording unit.

Other related hydraulically operated machines have been required toaccurately measure various materials to be loaded and carried, such asin U.S. Pat. No. 2,851,171 directed towards a material handling vehiclewith a pivotable front loading bucket. An hydraulic pressure responsivegauge is provided in the hydraulic system of this device and iscalibrated in units of weight. In that device the gauge is connected inan hydraulic series circuit with an hydraulic pressure snubber andgauged control valve. The gauge being in the hydraulic series with thelifting cylinder for the bucket. An analog-to-digital conversionemploying a transducer, or the like, is not provided. A pressure gaugeis difficult to keep calibrated and often is subjected to damage andinaccuracy during changeable weather conditions. The operation of thisprior art system creates vibration and instantaneous hydraulic pressuresurges so that a snubber is provided to dampen the effect, but requiresa long time period to effectively dampen and is not highly accurate.Such devices do not teach utilization in an hydraulic systemaccommodating a microprocessor for tabulating over time the tare weightsof a series of loads.

Systems for lowering loads onto a scale are known, such as in U.S. Pat.No. 3,612,490 where a skip loader is lowered by means of controlling theflow of hydraulic fluid from the lower end of an hydraulic cylinderwhile the loader is being lowered onto the weigh scale. An accuratemeasurement of loading in an hydraulic refuse container lifting systemis not provided and weighing in this patent is independent of anyhydraulic pressures.

A weighing system that provides for both dynamic and static weighingthat controls the ascent and descent of lifting arms, orcontainer-engageable lifting means, is not shown or suggested by theprevious weighing systems.

It is accordingly a primary goal of this invention to provide for theaccurate weighing of full and empty refuse containers by eliminating thevibration, pressure fluctuations, pressure surges and random shakingencountered in lifting heavy waste and refuse container loads.

It is another important goal of the invention to provide for acontrolled weighing step in the lifting and dumping of a refusecontainer whereby sensed gross and empty weight values may beelectrically signalled to a microprocessor wherein the tare weight maybe calculated and serially tabulated during the course of the dailyoperation of a refuse vehicle.

It is another important objective of the invention to eliminate theproblems with load cells and strain gauges previously used at themechanical arms of refuse lifting devices and instead implement aseparate hydraulic bypass system to the main hydraulic system, which isfluidly associated with the lifting circuit of the main system, wherebyaccurate calibrated readings may be made.

It is a further goal of the invention to provide for a controllinghydraulic bypass circuit that permits both manual and automatic weighingin conjunction with an analog/digital converting and microprocessingsystem.

It is yet another critical goal of the invention to provide a system forcontrolling the movement of a lift arm whereby accurate weights may besensed by a transducer during both static or dynamic weighing modes,depending on the software program used, whereby to be usable withmicroprocessors having either or both capabilities.

It is an allied goal of the invention to overcome the imprecision foundin dynamic weighing systems in the prior art by means of making possiblethe accurate calibration of a transducer by virtue of controlling over alimited path of motion the ascent or descent of the lifting arm assemblyof a refuse collection vehicle.

It is yet another object of the invention to implement a transducer in abypass hydraulic circuit which may be calibrated for different weightranges, and types of refuse containers, in conjunction with amicroprocessor that has numerous scales for the different ranges.

It is concomitantly a critical goal to provide for a weighing systemthat is reliable during the course of daily loadings and of dumpingcontainers into a refuse vehicle, which involves severe dynamic impacts,variable loading, extreme weather conditions and human error inpositioning the container.

It is an ultimate goal of the invention to provide for a weighing systemthat may be usable by lift cylinders that operate lift arms either bypushing or pulling them to pivot the lift arms during collection.

SUMMARY OF THE INVENTION

The invention may be summarized as comprising a bypass system bypassingthe lift circuit of the hydraulic lift cylinder of a refuse vehicle. Thebypass system including a flow rate control valve, a remote controlvalve, preferably operated by a solenoid and switch assembly controlledeither by the vehicle driver, or automatically by means of amicroprocessor, and further including a transducer providing an analogelectric signal in response to pressures developed in the bypass circuitfrom the lift circuit. The pressures developed and signalled by thetransducer are previously calibrated in the microprocessor to correspondto the weight lifted.

The system further includes proximity switch means and switch activatormeans, preferably in the form of striker pins, on the lift arms atreference and weighing locations so that the proximity switch isactivated to cause a signal to the driver when the lift arms are ateither position. Upon engaging a refuse container, the lift arms of thevehicle are moved upwardly through a first or weighing position wherebythe proximity switch may, for example, cause a signal light tomomentarily illuminate as the arms move past the first position to asecond or reference position, where the proximity switch is againactivated to re-illuminate the signal light. The operator then switcheson the remote control solenoid valve of the bypass system. The controlvalve slowly taps-off hydraulic fluid under pressure from the liftcircuit to release it to a reservoir and in a controlled manner causesthe lift arms and held container to move downwardly until the proximityswitch is and then re-activated when the load returns to the first, orweighing position. Upon seeing the signal light illuminated again, theoperator releases the switch and the control valve is closed. The nowsteadily-held container is statically weighed by means of the transducergenerating an analog signal corresponding to the pressure value to themicroprocessor or weighing instrument. Alternately, the load may bedynamically weighed during the end portion of the controlled downwardtravel with a microprocessor software program that stores and convertsto a digital readout the transducer signals over a period of time,usually about one-half second is sufficient. The controlled manner ofmovement obtained by the bypass circuit system and control valvesteadies the load over this range and eliminates the hydraulic surgesand variations, mechanical wobbling, equipment vibration, and otherdynamic factors that have created unreliability in previous measuringsystems. The system will be understood to be useful not only for refusecollection equipment, but a variety of hydraulic lifting devicesincluding log stackers, forklifts, bulldozer, end loaders, powershovels, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, consisting of FIGS. 1-6, like reference numerals areused throughout to refer to the same elements wherein:

FIG. 1 is an elevational view of a refuse vehicle with a lift armassembly engaging a refuse container resting on the ground;

FIG. 2 is the refuse vehicle of FIG. 1 showing the lift arm assemblyholding the container in an upper or reference position;

FIG. 3 shows the refuse vehicle after the lift arm assembly has loweredthe refuse container to a lower or weighing position for weighing thecontainer either empty or full depending upon the stage of theoperation;

FIG. 4 illustrates the positioning of the lift arm assembly uponemptying the container into the receptacle following ascent from thelower position shown in FIG. 3;

FIG. 5 is a schematic illustration of the electrical and hydraulicsystems of the refuse vehicle including the inventive bypass and controlvalve circuit system for controlling the movement of the lift armassembly; and,

FIG. 6 is an enlarged drawing of the transducer, remote control valveand flow control valve of the bypass circuit system as shown in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

To understand the apparatus and weighing process of the invention, theFigures will be explained with reference to the illustrated apparatusand process, which can provide optional forms making it possible for anoperator to either manually or automatically control the lifting andemptying of a refuse container, and control the signalling to amicroprocessor to serially weigh repeated gross and empty weights inorder to sum tare weights as the workday goes on. At the end of the day,the microprocessing system can tabulate to total weights collected andalso may connect to a printer to provide a printout billing record.Software programs to execute these functions are available.

The drawings show a refuse vehicle 10 in one known form of a motorizedrefuse collection vehicle for purposes of explaining the invention. Thevehicle 10 is a front loading type vehicle with hydraulically operatedlifting apparatus for seizing, holding, lifting and dumping a refusecontainer. A wide range of collection and lifting devices may beutilized with the invention, including stationary hydraulic liftingequipment wherein a container is brought to the lifting apparatus at acollection site instead of a vehicle going to the container. The presentinvention is useful for those lifting devices utilizing hydraulic liftsystems.

The invention is directed toward tapping off a lift circuit for a liftcylinder of the vehicle 10. The system will be understood in greaterdetail with later reference to the schematic illustrations in FIGS. 5and 6.

It will further be understood that the vehicle 10 hydraulically pivotsthe lifting arms by pulling on them. Other mechanisms may be designed topush a lift arm about a pivot point and the choice is a matter ofengineering particular to the apparatus designer. The present inventionis usable for either type of system whether pulling or pushing againstlift arms, but it is important to the present invention to tap-off fromthe lift circuit of the lift cylinder which is the hydraulic line thatpumps from a fluid reservoir to the lift cylinder--not the return lineof the lowering circuit. This is so that cylinder back pressure may bemeasured, which is a more accurate manner of measuring pressure. Thevehicle 10 has a cab 11, bed 12 and collection bin or hopper 13 mountedon the bed 12. An hydraulically operated lift assembly 14 is arranged atthe front of the vehicle 10 and has major components comprisingconventional yoke-like inverted U or J-shaped lifting arms 15 hingedlyarranged with the vehicle 10 at pivot pins 16 and pivotable by operationof lift cylinders 17. The lifting assembly 14 is engageable with refusecontainers by means of separately pivotable engageable arms 18 which arepivoted on arms 15 at pivot pins 19. In FIG. 1, a refuse container 20 isengaged by the engageable arms 18 extending through a sleeve or slottedbracket 21 attached at the side of the container 20. As would beunderstood the FIGS. 1-4 show only the left side of the vehicle 10 andthe right side is not shown since it would be substantially the samebecause the lift assembly 14 is generally symmetric.

Mounted on the interior side of the lift arm 15, and relatively close tothe pivot pin 16 are two striker pins 22, 23 which are provided to beactivator means for activating a magnetic proximity switch 24 at twoelevations of the lift assembly 14 reached during the lifting andemptying of the container 20. A proximity switch 24 is needed only onone lift arm 15. To the left of FIG. 1, two directional arrows are shownfor the sequenced movement of the container 20, which will be explainedhereinafter.

The interior of the cab 11 is generally outlined in dashed lines andfurther includes a set of hydraulic control levers 25 for operating thehydraulic lift assembly 14. The weighing operation and calculation isobtained by means of a weighing instrument 26, which will be furtherexplained in conjunction with the hydraulic control system of theinvention as being an onboard microprocessor controlled digitalinstrument.

On a portion of the lift arm 15, near pivot pin 19, are orthogonallyrelated leveling pins 27 and 28 which are visual indicators to theoperator in the cab 11 to aid in leveling the container 20 duringlifting by keeping them positioned in a certain way. The use of levelingpins is common practice in the industry. FIGS. 1-4 illustrate thearrangement of the refuse container 20 in four key positions duringlifting, weighing and dumping. FIG. 1 is the position at which therefuse vehicle 10 first moves forward to engage the engageable arms 18into the side sleeves 21. The container 10 is thus shown there restingon the ground, dock, warehouse floor, etc. The operator then activatesthe hydraulic system and causes lift cylinder 17 to pull on and pivotthe lift arm 15 to lift the container 20 to the position shown in FIG.2. As the container 20 is lifted the operator will usually level thecontainer 20 at or slightly before reaching the reference position ofFIG. 2. To reach the reference position in FIG. 2, strike pin 22 willhave once activated the proximity switch 24 which would operate a signallight in the cab to go on and then switch off as the strike plate 22moves past the proximity switch 24. Upon reaching the position in FIG.2, strike pin 23 contacts the proximity switch 24 to coincide with thearrival of the container 10 at the reference level of FIG. 2 and thesignal light in the cab is again illuminated to indicate to the operatorthat this position has been reached. Of course for manual operationother-type indicators can be used, such as an audible warning, videoscreen display, etc. In automatic operation, as will be discussed later,the proximity switch 24 may be directly wired to a weighing instrumentor microprocessor.

Upon rising to the reference position, the inventive hydraulic controlbypass system of the invention is engaged and the refuse container 20 issmoothly and steadily lowered to the weighing position shown in FIG. 3,at which point strike pin 22 contacts the proximity switch 24 tore-illuminate the signal light in the cab. This indicates to theoperator it is time to disengage the hydraulic control bypass system.The gross weight is automatically captured and retained in memory by theweighing instrument 26 as will be explained hereinafter. The grossweight is captured by the instrument and next the operator re-engagesthe standard hydraulic controls 25 to lift the container 20 from theposition in FIG. 3 continuously through the position of FIG. 2. Thesignal light in the cab would go off after leaving the position in FIG.3 and then switch on and off as it passes through reference point ofFIG. 2. Also, as the container moves through the reference point of FIG.2 the weighing instrument 26 automatically arms itself in the tare modeand is ready to receive a transducer signal for weighing the emptycontainer 20. The lift cylinder 17 ultimately pivots the lift arm 15 tobring the container 20 to the dumping position shown in FIG. 4. Therefuse and waste materials are dumped into the hopper 13. When thecontainer 20 is emptied, the operator activates the controls 25 to causethe hydraulic lift assembly 14 to move the container 20 downwardly untilthe striker pin 23 activates proximity switch 24 at the position in FIG.2 to illuminate again the signal light in the cab. The descent is thenstopped. The operator then will activate the hydraulic bypass controlsystem, and the container is slowly lowered to the weigh position ofFIG. 3. As it leaves the position of FIG. 2 the striker pin 23 moves outof contact with the proximity switch 24 and the signal light is off,until the refuse container 20 returns to the position of FIG. 3. At theweigh position the strike pin 22 activates the proximity switch 24 andilluminates the light to provide another weigh signal to the operator.Another transducer-generated analog signal from the hydraulic controlbypass system is sent to the weighing instrument 26. The empty weight ofthe container is then captured. The microprocessor makes a tare weightcalculation for the contents that were dumped into the receptacle 13 andthe value is recorded, stored and tabulated for later retrieval,printout, and for invoicing the customer.

Therefore, for static weighing the weight is always captured at thelocation of the container 20 shown in FIG. 3 for both full and emptycontainer weights. A continuing sequence of containers 20 all willdescend in the same controlled steady manner from the reference positionof FIG. 2 to the weighing position in FIG. 3 so that reliable weightvalues are recorded.

Turning now to FIGS. 5 and 6, the bypass control system of the inventionis generally designated at reference numeral 29 and the standardhydraulic system for the lifting assembly 14 is generally designated atreference numeral 30. The bypass control system 29 taps into thehydraulic system 30 and controls the motion of the lift arm 15 forweighing full and empty containers 20. The hydraulic system 30 includesa lift circuit line 31 for driving the lift cylinder 17 under pressure.Flow through the lift circuit 31 is controlled by a manually controlledvalve 32 that is operable by the operator from the cab at the controls25. A relief valve 33 is interposed between the main control valve 32and a pump 34 for pumping the hydraulic fluid through the system from areservoir 35. For lowering the lift arm 15, fluid is retracted from thelift cylinder 17 through a lowering circuit 36 back through the maincontrol valve 32 to a main return line 37 communicating with thereservoir 35. The bypass control system 29 taps-off the lift circuit 31at 38 to a bypass line 39 and ultimately returns the fluid back to thereservoir 35 through a bypass return line 40 connected to the mainreturn line 37 at 41. Creating flow through the bypass control system 29is obtained by the operation of a normally closed remote control valve42 that feeds to a normally open pre-set flow rate control valve 43. Atransducer 44 resides along the bypass line 39 and responds to thepressure in the bypass line 39 to generate an analog electrical signalto the microprocessor of weighing instrument 26. In the illustrativeembodiment, a 3000 psi rated hydraulic transducer is used. The remotecontrol valve 42 is, in one form of the invention, a manually operatedsolenoid valve that is normally closed. It is energized by a switch inthe cab that the operator activates upon receiving the light signal atthe activation of the proximity switch 24 by the striker pin 23 at thereference position shown in FIG. 2. Electrical power for the remotecontrol valve 42 is provided by the usual battery pack of the vehicle10. A safety or "deadman's" switch 46 is operated by a battery 45.

When the container 20 reaches the reference position of FIG. 2, theoperator activates the remote control valve 42 by depressing a switch toopen the valve 42 and thereby hydraulic fluid is tapped-off the liftcircuit line 31 at connection 38 to flow through the bypass line 39 andoutwardly of the system 29 through bypass return line 40 in a controlledand relatively slow descent rate set at the flow rate control valve 43.The rate of descent is significantly slower and smoother than providedby the main control valve 32. Thereby, erratic pressure surges, rockingand dynamic thrusts on the container 20, are substantially eliminated sothat during the descent from the reference position to the weighingposition a very steady loading force is experienced by the lift arms 15.An even hydraulic flow in the lift circuit 31 is created and a steadypressure value, or rate, during descent is sensed by the transducer 44.In this way, the weighing instrument 26 may be precisely calibrated fordifferent size containers and for pressures caused by different rangesof weight. The calibration is very reliable because subsequent actualcontainer handling are always controlled in the same way in the descentfrom the reference point to the weighing point. By virtue of the signalscaused by the proximity switch at those two locations, the lift arms 15repeatedly are caused to move through substantially the same path andrelative speed for each type of container 20. The weight is alwayscaptured at substantially the same position, resulting in accuratecalculation of the net weights of the refuse material dumped to thereceptacle 13.

One weighing instrument particularly suitable for use is made byWray-Tech Instruments, Inc., Downers Grove, Ill., under model nos.WT4000/6000/8000. These are onboard microprocessor controlled digitalweighing instruments.

To further explain the modes of operation of the bypass control system29, it should be understood that as a load in the container 20 israised, the pressure presented to the transducer 44 consists ofcontributions from fluid movement in the lift circuit 31, friction, theweights of the mechanical components of the lift assembly 14, and theweight of the load in container 20. In the manual mode of operation, theload is not weighed as it first passes through the weighing position ofFIG. 3, but instead moves directly to stop at the reference position ofFIG. 3, whereupon the proximity switch 24 is activated by the strikerpin 23 to illuminate a signal light in the cab. Preferably just at orbefore rising to the reference position, the operator will level thecontainer 20 so that for each load the same angle of inclination of thecontainer is achieved. Then, the operator activates a switch to energizethe normally closed remote control valve 42 to slowly bleed hydraulicfluid under pressure through the bypass line 39, the transducer 44 andback to the reservoir 35 until the proximity switch 24 goes off and thenon again as it is re-activated by striker pin 22, so that the signallight is illuminated for the operator to stop the slowly descendingcontainer 20 at substantially the same point each time. The weighinginstrument 26 automatically captures the weight. The bypass controlsystem 29 is operable with a microprocessor whereby to be manuallyoperable for both static and dynamic weighing. The difference betweenthe static and dynamic procedures is mainly that the static weighingrequires the load to be held for no more than about five seconds in theweighing position while the dynamic method captures the weight as itmoves through the weighing position of FIG. 3 from the referenceposition of FIG. 2. Both static and dynamic weighing require the load tobe lowered from the reference position to the weighing position.Commercially available software systems allow a microprocessor to beprogrammed either for static or dynamic weighing. In both static anddynamic weighing methods, the weighing instrument automatically armsitself to accept, capture and record gross and tare weights. The remotecontrol valve 42, in the exemplary embodiment, is operated manually. Indynamic weighing, the weighing instrument 26 converts continuous analogsignalling from the transducer to display a digital readout and acalculated weight value is finally stored upon reaching the weighingposition. The weighing process of the invention centers on thecontrolled lowering of the load from the reference point to the weighingposition, in either mode. For dynamic weighing, it is not required thatthe load be held in a position at FIG. 3 since a software program willcalculate the weight at a set time sequenced after the container leavesthe reference point, and in the described system is about a one halfsecond time interval.

The main hydraulic system 30 is operated at controls 25 and has theability to override the remote control valve 42 to initially lift thecontainer 20 to the reference point.

The static weighing mode requires holding in the weighing position untilthe gross weight is accurately captured, usually about 3 to 4 seconds.In dynamic weighing the load is allowed to continue falling until thegross weight is captured, as stated above, about one half second whenusing the WT4000/6000/8000 microprocessor. The tare weighing by theweighing instrument 26 can also be automatically done by thereactivation of the proximity switch 24 as the container 20 is raisedand dumped after the gross weight has been captured. Weighing in theautomatic mode is then completed by moving the empty container 20 to thereference position and stopping there, whereupon the signal is generatedby the striker pin 23 activating the proximity switch 24. The operatornext activates the remote control valve 42 to allow the load to fall tothe weighing position where the tare weight is automatically capturedupon signalling caused by the re-activation of the proximity switch atthe weigh position and the net weight is displayed on a digital displayof the weighing instrument 26.

Provided that the components other than the load in the container 20 canbe kept at the levels which exist at calibration, the pressure measuredby the transducer 44 can accurately represent the weight of the loadbeing lifted. In order to achieve this, the speed of the operation andthe tilt of the engageable arms 18 relative to the container 20 must becontrolled. An onboard microprocessor digital weighing instrument 26such as the WT4000/6000/8000 model, will capture the weight of the loadat the weighing position where the machine-generated pressurecontributions are known.

Known microprocessing software can provide a variety of ways foraccumulating the totals, such as per customer per day, or per month inprintout form, as would be understood. Also, useful microprocessors forthe invention preferably will have multiple scales for correspondingpressure calibrations of different size containers and loading ranges,so that fluid pressures involving different machinery-generatedvariations may be obtained for changeable load conditions. Multiplecalibration scales are also necessary for enhanced accuracy due todifferent ways in which the engagement arms 18 might engage a variety ofengageable sleeves or brackets of refuse containers.

Accordingly, a unique and efficient bypass control system is provided toaccurately and reliably calculate the full and empty weight of a refusecontainer as it is loaded and emptied into a refuse collection vehicle,or the like.

While the foregoing description is provided in connection with oneembodiment and several described alternative modes of use of theinvention, it will be understood that a wide range of equivalents fallwithin the scope of the claims appended hereto.

What is claimed is:
 1. A motion control method for generating reliableanalog electrical signals from a pressure transducer means and providinganalog signals responsive to hydraulic fluid pressure caused by liftinga weight by means of an hydraulic lift assembly of a refuse collectionvehicle, said method comprising the steps of:tapping off hydraulic fluidunder pressure from the lift circuit of an hydraulic lift assembly of arefuse collection vehicle; bypassing said tapped off hydraulic fluidthrough an hydraulic bypass circuit; lowering a weight lifted by thehydraulic lift assembly; directing said tapped-off hydraulic fluid tohydraulic pressure transducer means sensing the pressure in thehydraulic bypass circuit and generating an analog electrical signalcorresponding to the weight being lowered by said hydraulic liftassembly; communicating said analog signal to an analog/digitalconverter means; and, creating a digital record of the weight.
 2. Themethod as claimed in claim 1 wherein the step of generating of an analogelectrical signal from said transducer means occurring dynamically whilesaid hydraulic lift assembly lowers the weight.
 3. The method accordingto claim 1 wherein said tapping off step is preceded by opening anormally closed valve in the hydraulic bypass circuit.
 4. The methodaccording to claim 3 including prior to the tapping off step, generatingan electrical signal when a lifted weight is lifted to a referenceposition.
 5. The method according to claim 1 wherein the generating ofan analog electrical signal occurring as said weight is statically heldby said hydraulic lift assembly.
 6. A motion control method forgenerating reliable analog electrical signals from a pressure transducermeans and providing analog signals responsive to hydraulic fluidpressure caused by lifting a weight by means of an hydraulic liftassembly of a refuse collection vehicle, said method comprising thesteps of:opening a normally closed valve in an hydraulic bypass circuit;tapping off hydraulic fluid under pressure from the lift circuit of anhydraulic lift assembly of a refuse collection vehicle into saidhydraulic bypass circuit; lowering a weight lifted by the hydraulic liftassembly; directing said tapped-off hydraulic fluid to hydraulicpressure transducer means and generating an analog electrical signalcorresponding to the weight being lifted by said hydraulic liftassembly; communicating said analog signal to an analog/digitalconverter means; and, creating a digital record to the weight.